Telecommunications networks use a variety of technologies to transmit signals between subscribers. These technologies include both analog and digital communications. One digital technology used to communicate signals in telecommunications networks is referred to as asynchronous transfer mode (ATM). ATM technology is a packet-based technology that transports data as payload in packets known as cells.
Typically, ATM packets or cells are 53 bytes long, including overhead and payload. When user data exceeds the payload capacity of an ATM cell, the user data is divided into smaller portions and transported using multiple cells as is known in the art.
A typical communication network includes a physical medium, e.g., copper wire, optical cable, wireless medium, or other appropriate physical medium, for transporting cells between ATM equipment. Conventionally, a transmission convergence (TC) layer is used to make the transition between the ATM-based equipment and the physical medium. For example, when receiving cells, the TC layer conventionally looks for a cell boundary and then counts a selected number of bytes (typically 53) and tests for another cell boundary. The TC layer then converts the received bytes into a cell for use by the ATM-based equipment.
In some systems using ATM cells, it is desirable to transport additional information between ATM equipment connected over a physical link. This additional information is sometimes referred to as “out-of-band” information. It is desirable to be able to carry this information between the ATM-based equipment within the ATM cells. This out-of-band information is typically information that is not provided for in the standard ATM cell. Further, the size of such out-of-band data may change from time to time. Unfortunately, a conventional TC layer is designed for a specific, usually standard, cell size. Thus, if an ATM product is updated to include the use of additional out-of-band information, the TC layer typically has to be redesigned to account for the new out-of-band information to be passed over the physical medium.
Therefore, there is a need in the art for reducing the complexities associated with changing the size of packets in a packet-based communication system.